Pathways involved in PTH-induced rise in cytosolic Ca2+ concentration of rat renal proximal tubule

Abstract

Parathyroid hormone (PTH) raises cytosolic Ca2+ concentration ([Ca2+]i) in isolated or cultured renal proximal tubule cells. The pathways through which this action is mediated are not fully delineated. This study explored these pathways utilizing fura 2. [Ca2+]i of freshly prepared renal proximal tubular cells increased from 150 +/- 3.6 to 281 +/- 9.0 nM after the exposure to 10(-7) M angiotensin II, which served as a positive control. Both PTH-(1-84) and PTH-(1-34) produced a dose-dependent rise in [Ca2+]i. The effects of both moieties were similar up to 10(-7) M, but with higher doses the rise in [Ca2+]i with PTH-(1-84) was greater (P < 0.01) than with PTH-(1-34). This effect of the hormone occurred in the presence or absence of calcium in the media, but the rise in [Ca2+]i was significantly greater in the presence of calcium. The PTH-induced rise in [Ca2+]i was markedly inhibited by PTH antagonist [Nle8,18,Tyr34]bPTH-(7-34)-NH2 (bPTH is bovine PTH), verapamil, or nifedipine. 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, increased [Ca2+]i of cells, but its effect was less than PTH. Staurosporine abolished the TPA effect and partially inhibited that of PTH. A G protein activator raised [Ca2+]i, whereas a G protein inhibitor and pertussis toxin partially blocked the effect of PTH. Sodium or chloride channel blockers or sodium-free media did not modify the effect of PTH.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation by Parathyroid Hormone of a NHERF-1-assembled Complex Consisting of the Parathyroid Hormone I Receptor, Phospholipase Cβ, and Actin Increases Intracellular Calcium in Opossum Kidney Cells

“…The receptor-mediated calcium channel blocker SKF96365 (26) inhibits the PTH-mediated increase in [Ca 2ϩ ] i in a dose-dependent manner (Fig. 3C), which supports this conclusion, and is consistent with published data that PTH predominantly mediates an influx of calcium ions in wild-type OK cells (24) and PCT cultures (16,27,28). The phospholipase C inhibitor U73122 and pertussis toxin also block the PTHmediated increase in [Ca 2ϩ ] i (Fig.…”

“…PTH has been shown repeatedly to increase [Ca 2ϩ ] i either by causing calcium release from intracellular stores or by increasing calcium influx from the extracellular space in many cell models (31 renal cell models (24,28) and with our earlier report demonstrating that the NHERF-2-assembled PTH1R activates PLC by stimulating a member of the G i/o family of G proteins (17). Overall, PTH signaling in OKH cells with stable expression of NHERF-1 is consistent with PTH-mediated responses displayed in PCT and wild-type OK cells.…”

Effect of thyroparathyroidectomy on urinary acidification in diabetic rats

“…A significant rise in [Ca 2+ ]i was also observed in rat polymorphonuclear cells incubated with a high glucose medium (36). On the other hand, PTH also causes a rise in [Ca 2+ ]i in many cells, including renal tubular cells (37,38). Thus, a fall in [Ca 2+ ]i could be expected in TPTX.…”

Parathyroidectomy Does Not Affect mRNA of PTH-PTHrP Receptor in Kidney, Liver, and Heart

“…These samples were used for the preparation of RNA. The other kidney was used for the isolation of renal proximal tubular cells enploying a modification of the method of Vinay et al [7], The details of this technique have been previously reported from our laboratory [8]. [Ca2*], was measured using Fura 2-AM at excita tion wavelengths of 340 and 380 nm and an emission wavelength of 510 nm.…”

“…Calculation of [Ca2+]i was made using the equation of Grynkiewicz et al [9], The details of this method have been reported by us previously [8], R15B plasmid encoding the full length of the rat PTH-PTHrP receptor was kindly supplied by Dr. Geno V. Segre of the Massachu setts General Hospital (Boston, Mass., USA). We prepared a 1,200-bp fragment of the cDNA PTH-PTHrP receptor as previously reported [1], Total RNA was isolated from kidney, liver, and heart by acid guanidinium thiocyanate-phenol-chloroform extraction as described by Chomczynski and Sacchi and later modified by them using the trizol reagent [10].…”